The present invention relates to an improvement in walk-behind cultivators.
Common walk-behind cultivators operate by rotation of tillage tines provided on rotor shafts, being propelled with the tillage tines. Those cultivators are called front-tine cultivators. In recent years, however, front-rotary cultivators, that is, walk-behind cultivators with tillage tines arranged forward of the bodies provided with driving wheels have been developed.
Having the tillage tines at the front of the bodies, the front-rotary cultivators facilitate cultivation in headlands, allowing operators to look forward during operation, providing good workability, and thus attracting attention (See, e.g., Japanese Patent No. 3015821 and Japanese Utility Model Laid-Open Publication No. SHO-56-97903).
The words xe2x80x9cheadlandsxe2x80x9d mean areas left unplowed by a cultivator cultivating a rectangular-shaped field, moving back and forth in parallel with one side thereof, for example, because it temporarily stops working at the opposite ends of the field for turning or the like.
A cultivator in Japanese Patent No. 3015821 is called a down-cut cultivator with tillage tines rotated from the upper front of a traveling direction toward the ground and is mainly used to break up soil.
A cultivator in Japanese Utility Model Laid-Open Publication No. SHO-56-97903 is called an up-cut cultivator with tillage tines rotated from the upper rear of a traveling direction toward the ground and is mainly used to weed a field.
As an example of such front-rotary cultivators, the cultivator of Japanese Patent No. 3015821 will be generally described with reference to FIG. 16 hereof.
A front-rotary cultivator 200 shown in FIG. 16 is a walk-behind cultivator with a transmission case 203 provided below a body 202 to which an engine 201 is mounted, the transmission case 203 being integrally molded with a rear mission case 204 and a front rotary case 205, a pair of left and right driving wheels 207, 207 mounted on an axle 206 protruded from a rear portion of the mission case 204, a rotary countershaft 208 provided in a front portion of the mission case 204, a plurality of tillage tines 210 mounted on a rotor shaft 209 protruded from a front portion of the rotary case 205, and a chain 213 running in the rotary case 205 between a driving sprocket 211 of the rotary countershaft 208 and a driven sprocket 212 of the rotor shaft 209.
The engine 201 is a horizontal engine with an output shaft 214 protruded laterally. A belt 218 runs between a driving pulley 215 mounted on the output shaft 214 and a driven pulley 217 mounted on an input shaft 216 protruded from the side of the mission case 204 to transmit the power of the engine 201 to the transmission. The power of the engine 201 can thus drive the pair of left and right driving wheels 207, 207 via the axle 206 and drive the tillage tines 210 via the rotary countershaft 208, chain 213 and rotor shaft 209.
The tillage tines 210 of the front-rotary cultivator 200 are arranged in four rows across the width of the body 202 (across the two sides of the figure sheet). All the tillage tines 210 rotate with the rotor shaft 209 in one direction for cultivation. Reference numeral 219 denotes a tension roller as a main clutch and 220 a handle bar.
Cultivation with the tillage tines 210 can cause a so-called dashing phenomenon (or jumping phenomenon) in which the cultivation reaction force causes the tillage tines 210 to bound upward. The dashing phenomenon caused reduces the linearity in travel of the cultivator 200, resulting in insufficient cultivation performance and poor finish of cultivation. This tendency is more noticeable especially as the cultivator 200 is lighter in weight.
The above conventional art arranges the engine 201 between the rear axle 206 and the front rotor shaft 209 to shift the center of gravity of the cultivator 200 forward, thereby to apply part of the weight of the engine 201 to the tillage tines 210. As a result, the degree of digging of the tillage tines 210 into the ground Gr21 can be somewhat increased and the occurrence of the dashing phenomenon can be somewhat prevented.
Only with such a structure, however, there is a limit to the increase in degree of digging of the tillage tines 210 and the prevention of the dashing phenomenon. To solve the problem, it seems possible to arrange the engine 201 or a heavy load such as a counterweight in front of or above the tillage tines 210 to increase the distribution of weight to the tillage tines 210. The center of gravity of the cultivator 200 is, however, too much offset forward, making the handle bar 220 heavier. Especially in the operation of pushing down the handle bar 220 to lift the tillage tines 210 to turn the cultivator 200, the pushing-down force is increased, reducing the operability. Only changing the center of gravity of the cultivator 200 forward thus inexpediently increases the workload of the operator.
Thus desired is a front-rotary cultivator with tillage tines arranged at the front of the body equipped with driving wheels, being able to prevent the occurrence of the dashing phenomenon, increase cultivation performance and also reduce the workload of the operator.
According to the present invention, there is provided a walk-behind cultivator, which comprises: a body; an engine provided on the body; left and right driving wheels provided to the body and driven by the engine; and a plurality of tillage tines provided at the front of the body and driven by the engine, the tillage tines comprising: a plurality of forward-rotating tines arranged in the center of the width of the body; and a plurality of reverse-rotating tines arranged outward of the forward-rotating tines in the transverse direction of the body, the reverse-rotating tines being arranged in the same phase in a side view.
Arranging the forward-rotating tines of the tillage tines in the center of the body width and arranging the reverse-rotating tines transversely outward of the forward-rotating tines allow the forward-rotating tines to (forwardly) rotate from the upper front of the traveling direction toward the ground and the reverse-rotating tines to (reversely) rotate from the upper rear of the traveling direction toward the ground.
The direction of the cultivation reaction forces against the forward-rotating tines is forward and upward of the traveling direction of the walk-behind cultivator, that is, opposite to the rotation direction of the forward-rotating tines. The direction of the cultivation reaction forces against the reverse-rotating tines is rearward of the traveling direction of the walk-behind cultivator, that is, opposite to the rotation direction of the reverse-rotating tines. The cultivation reaction forces against the forward-rotating tines and the cultivation reaction forces against the reverse-rotating tines act in opposite directions.
When all the tillage tines are forward-rotating tines, the cultivation reaction force is larger, making it difficult to prevent the occurrence of a dashing phenomenon due to the cultivation reaction force. In this invention, the cultivation reaction force arising from cultivation with the forward-rotating tines can be cancelled to some extent by the cultivation reaction force arising from cultivation with the reverse-rotating tines. As a result, the occurrence of a dashing phenomenon can be prevented.
With the walk-behind cultivator being propelled, the forward-rotating tines in the center of the body width can rotate forward to dig into the ground for cultivation, digging out the cultivated soil rearward of the cultivator body.
Arranging the reverse-rotating tines in the same phase in a side view allows the reverse-rotating tines arranged transversely outward of the forward-rotating tines to rotate reversely, with the walk-behind cultivator being propelled, to simultaneously dig into the ground, digging out the cultivated soil forward of the cultivator body.
Simultaneous digging of the reverse-rotating tines into the ground can also increase the degree of digging as compared with differential digging. As a result, the depth of plowing with the reverse-rotating tines is increased, increasing cultivation performance.
Simultaneous digging of the reverse-rotating tines into the ground can make the cultivation reaction forces against the reverse-rotating tines approximately equal. The approximately equal cultivation reaction forces can prevent the unbalanced occurrence of a dashing phenomenon and also prevent the occurrence of a pitching phenomenon (phenomenon in which the cultivator swings back and forth like a seesaw). This prevents snaking of the cultivator, increasing its travel linearity, steerage and workability, and improving cultivation finish.
Even when the cultivator has a light weight, it is not necessary to dispose the engine or a heavy load such as a counterweight in front of or above the tillage tines, increasing the weight distribution to the tillage tines so as to increase the degree of digging of the tillage tines to prevent a dashing phenomenon. Therefore, in the operation of pushing down an operating handle to lift the tillage tines during turn of the cultivator, the pushing down force is not increased. This can reduce the workload of the operator, increasing steerage.
In this invention, the forward-rotating tines are preferably arranged in the same phase in a side view.
Arranging the forward-rotating tines in the same phase in a side view and arranging the reverse-rotating tines in the same phase in a side view allow the forward-rotating tines in the center of the body width to, with the walk-behind cultivator being propelled, forwardly rotate to simultaneously dig into the ground for cultivation, digging out the cultivated soil rearward of the cultivator body. The reverse-rotating tines arranged transversely outward of the forward-rotating tines are allowed to rotate reversely to simultaneously dig into the ground, digging out the cultivated soil forward of the cultivator body.
The simultaneous digging of the forward-rotating tines into the ground can increase the degree of digging as compared with differential digging. The simultaneous digging of the reverse-rotating tines into the ground can also increase the degree of digging. This results in an increase in the depth of plowing with the forward-rotating tines and the reverse-rotating tines, further increasing cultivation performance.
Further, simultaneous digging of the forward-rotating tines into the ground can make the cultivation reaction forces against the forward-rotating tines approximately equal. The same applies to the reverse-rotating tines. The approximately equal cultivation reaction forces allow further prevention of the unbalanced occurrence of a dashing phenomenon and also allow prevention of the occurrence of a pitching phenomenon (phenomenon in which the cultivator swings back and forth like a seesaw).
Furthermore, the simultaneous digging of the forward-rotating tines into the ground with the simultaneous digging of the reverse-rotating tines into the ground can make approximately equal the left and right cultivation reaction forces acting on the cultivator. This also enables preventing the occurrence of a rolling phenomenon (phenomenon in which the cultivator rolls around the longitudinal axis passing through the center of gravity of the cultivator). This can further prevent snaking of the cultivator, increasing travel linearity and steerage, further increasing the workability, and also improving cultivation finish.
Further, in this invention, the left and right driving wheels are preferably arranged rearward of the reverse-rotating tines. In the cultivator of the present invention adopting the front-rotary system, the driving wheels are arranged rearward of the tillage tines. Arranging the driving wheels rearward of the reverse-rotating tines to dig out the cultivated soil forward of the cultivator body allows the driving wheels to run over the ground dug down with the reverse-rotating tines. This can increase the degree of settling of the driving wheels, maintaining the cultivator horizontally. Thus stable cultivation is provided. Since the position of the engine is also horizontal, the oil surface of a lubricant in the engine is not slanted. Thus smooth lubrication of the engine is provided.